Commutator brush holder



Aug. 29, 1967 M. p. BURROWS ETAL 3,339,098

COMMUTATOR BRUSH HOLDER.

. Filed March .2, 1965 INVENTORS v MILFORD D. BURRO F/G.4 WILLIAM J. CONLO PETER H. MORGANSON W, WM

ATTORNEYS United States Patent 3,339,098 COMMUTATOR BRUSH HOLDER Milford D. Burrows, Avon, William J. Conlon, New

Britain, and Peter H. Morganson, Winsted, Conn., assignors to The Stanley Works, New Britain, Conn., a corporation of Connecticut Filed Mar. 2, 1965, Ser. No. 436,559 2 Claims. (Cl. 310-239) ABSTRACT OF THE DISCLOSURE The assembly of this invention includes a brush and an elongated body having opposite end openings and a generally rectangular guideway therebetween extending through the body with rear guideway portion of enlarged size relative to the front end opening and defining internal coplanar shoulders adjacent thereto. In addition, a longitudinal slot is formed in the body to extend along one side of the guideway through which a brush terminal is received for sliding movement in the enlarged rear guideway portion to an extent limited by the internal shoulders.

This invention generally relates to a brush assembly for electrical machines and is more specifically directed to a holder of a brush assembly for supporting a commutator brush.

A primary object of the present invention is to provide an improved commutator brush holder, for use in an electrical machine, which is particularly suited to securely retain the usual brush terminal within the holder after the brush is worn down by its sliding contact with the commutator, and even with the brush discharged from its holder during the operation of the electrical machine, so as to prevent undesirable and possibly dangerous electrical shorting between the brush terminal and parts of the machine.

Another object of the present invention is to provide a commutator brush assembly incorporating an improved brush holder for attaining the objects stated above and which additionally has notable utility in maintaining proper brush support and alignment and to effect smooth and uniform commutation despite manufacturing variations in the brush assembly and in the commutator.

A further object of the present invention is to provide an improved commutator brush holder which is simple in construction, durable in use and economical in manufacture and which is adapted for convenient assembly and replacement of the brush.

Other objects will be in part obvious and in part pointed out more in detail hereinafter.

The invention accordingly consists in the features of construction, combination of elements and arrangement of parts which will be exemplified in the construction hereafter set forth and the scope of the application which will be indicated in the appended claims.

In the drawing:

FIG. 1 is a side view of a brush assembly of the present invention in association with a commutator illustrated in part in phantom;

FIG. 2 is an enlarged longitudinal view, partly broken away and partly in section, of the brush assembly of FIG. 1;

FIG. 3 is a transverse section view of a holder of the assembly taken along line 3-3 of FIG. 2; and

FIG. 4 is a transverse section view, partly broken away, taken along line 4-4 of FIG. 2.

Referring now to the drawing in deail, it will be understood that the commutator brush assembly of the present invention is designed to be secured by suitable holding means in the structure of which it forms a part such as -poration under the tradename to be satisfactory.

ICC

that of an electrical motor, for example. A brush holder or box, generally designated by the numeral 10, is preferably molded of a suitable nonconductive material to provide a relatively rigid construction. In this regard, the resinous molding compound sold by Allied Chemical Cor- Plaskon has been found As illustrated, the brush box 10 has openings at the forward, or commutator end of its body and at the rear end of the body and an elongated brush guideway 12 extends between the openings. The brush guideway 12 is suitably dimensioned and configured for receiving a brush, or current collector, generally designated 14, which is shown as being'o-f rectangular section, and for this reason the brush guideway is of generally conforming rectangular cross section for properly supporting and guiding the brush for rectilinear movement within the brush box.

The brush 14, formed of a conductive material such as carbon, is held in place with its inner end retained inside the hollow brush box 10. The opposite or outer end of the brush projects outwardly from the brush box so as to ride on the surface of a commutator 16 (illustrated in phantom in FIG. 1) which is supported in a well known manher for rotation relative to the brush box 10. The brush 14 is adapted as hereafter described to be electrically con nected to a suitable lead such as that provided by the flexible lead wire 18.

In accordance with one aspect of the invention, a plurality of transverse abutments or internal shoulders are formed inside the brush box 10 with rearwardly facing coplanar surfaces 20 extending transversely to the longitudinal axis of the brush guideway. More specifically, three sides of the brush guideway 12 are counterbored to form a plurality of elongated, medial arcuate surfaces 22 extending coaxially with the guideway 12 forwardly from the rear end of the brush box and terminating adjacent its commutator end to provide the rearwardly facing surfaces 20. The described structure thus provides a forward guideway portion of relatively short longitudinal dimension and of rectangular cross section and which opens into a coaxially extending rear guideway portion of enlarged cross section.

The remaining side of the brush guideway is provided with an elongated slot 24 extending longitudinally from the rear end of the body and terminating, in the illustrated specific embodiment, between the rearwardly facing surfaces 20 and the forward commutator end of the brush box to provide a strengthening member 25 which may be removed entirely, if desired.

A cap, generally designated 26, is detachably mounted on the rear end of the brush box and includes a generally rectangular flange 28 extending forwardly from the periphery of a rear cover plate 29 to provide a shallow boxlike body open at its forward end. Extending inwardly from the inner surfaces of each of four sides of the rectangular flange 28 is a locking shoulder having a forward edge which is tapered or chamfered with the forward edge 30 of the flange 28 to provide a camming surface for snap ping engagement over correspondingly tapered peripheral flanges 32 integrally molded with the brush box at its rear end. The cap 26 is preferably formed of a high strength, durable material having excellent electrical resistance, such as the polycarbonate plastic Lexan sold by General Electric Company.

Seated on the inside face of the rear cover plate 29 is a compression coil spring 34 which is received in the counterbore in the rear received in the counterbore is a suitable brush terminal 36, such as the illustrated flat eye ring having a radially extending lead clamp 38 for gripping the lead wire 18. whereby an electrical connection to brush 14 is established by snugly fitting the brush terminal 36 over a reduced end portion of the brush box. Also i brush and its terminal 36 forwardly and thereby maintains the brush in electrical contact with the commutator. Accordingly, as the sliding contact with the commutator wears down the brush, the brush is moved forwardly in the guideway 12 to compensate for the brush wear, the brush terminal 36 being longitudinally movable within the slot 24 provided in the side of brush box 10.

By virtue of the described structure, after the forward rectangular portion of the brush is worn down substantially by the commutator, the brush terminal 36 engages the rearwardly facing surfaces 20 which thereupon cooperate with the coil spring 34 to securely retain the brush terminal 36 in a fixed position to positively stop the terminal 36 against further forward movement. If the brush is discharged from the brush box, even partial escapement of the brush terminal 36 from brush box is prevented. Accordingly, the commutator brush assembly is completely safe from dangerous shorting between the brush terminal and parts of the motor. I

Moreover, the previously described arcuate surfaces 22 longitudinally extending in the enlarged rear guideway portion serve to receive accumulated carbon dust, dirt and other foreign matter and, additionally, to accommodate brush warping, heat distortion and the like, and thereby to support the brush for rectilinear movement without binding of the brush within its holder.

Finally, the commutator brush assembly of the present invention may be easily assembled, and the brush terminal and the spring may be readily removed from and reinserted into the rear of the brush box in proper engagement with the brush simply by removing the cover.

As will be apparent to persons skilled in the art, various modifications and adaptatons of the structure above-described will become readily apparent without departure from the spirit and scope of the invention, the scope of which is defined in the appended claims.

We claim:

1. A brush assembly for conducting current from a rotating current collector and comprising a brush of conductive material having an end portion with leading and trailing edges engageable with a current collector, a brush holder having an elongated body of nonconductive material with a forward end and a rear end, the body having openings at its opposite ends and a generally rectangular guideway extending longitudinally therebetween through the body with three sides of the guideway having counterbored medial sections coaxially extending forwardly from the rear end of the body and terminating adjacent its forward end to provide a rear guideway portion of enlarged cross section with respect to the opening at the forward end of the body and internal shoulders with rearwardly facing coplanar surfaces at the forward termination of the enlarged rear guideway portion, the body having a longitudinal slot formed therein along the remaining side of the guideway and extending forwardly from the rear end of the body, a brush terminal extending through the longitudinal slot for receipt in the rear guideway portion for electrical connection to the brush, a spring in the rear guideway portion for maintaining the brush terminal in electrical connection with the brush, the internal shoulders coacting with the spring to engage the brush terminal therebetween and to firmly retain the brush terminal within the rear guideway portion after the brush is completely worn, and a snap-on cover of nonconductive material removably mounted on the rear of the body for closing the same and providing a seat for the spring.

2. The brush assembly of claim 1 wherein the longitudinal slot in the brush holder is contained in a plane perpendicular ot the leading and trailing edges of the brush.

References Cited UNITED STATES PATENTS 1,970,604 8/ 1934 Henry 310-247 2,045,293 6/ 1936- Carlson 310-245 3,108,201 10/ 1963 Summerfield 310247 FOREIGN PATENTS 732,470 6/ 1955 Great Britain.

MILTON O. HIRSHFIELD, Primary Examiner.

D. F. DUGGAN, Assistant Examiner. 

1. A BRUSH ASSEMBLY FOR CONDUCTING CURRENT FROM A ROTATING CURRENT COLLECTOR AND COMPRISING A BRUSH OF CONDUCTIVE MATERIAL HAVING AN END PORTION WITH LEADING AND TRAILING EDGES ENGAGEABLE WITH A CURENT COLLECTOR, A BRUSH HOLDER HAVING AN ELONGATED BODY OF NONCONDUCTIVE MATERIAL WITH A FORWARD END AND A REAR END, THE BODY HAVING OPENINGS AT ITS OPPOSITE ENDS AND A GENERALLY RECTANGULAR GUIDEWAY EXTENDING LONGITUDINALLY THEREBETWEEN THROUGH THE BODY WITH THREE SIDES OF THE GUIDEWAY HAVING COUNTERBORED MEDIAL SECTIONS COAXIALLY EXTENDING FORWARDLY FROM THE REAR END OF THE BODY AND TERMINATING ADJACENT ITS FORWARD END TO PROVIDE A REAR GUIDEWAY PORTION OF ENLARGED CROSS SECTION WITH RESPECT TO THE OPENING AT THE FORWARD END OF THE BODY AND INTERNAL SHOULDERS WITH REARWARDLY FACING COPLANAR SURFACES AT THE FORWARD TERMINATION OF THE ENLARGED REAR GUIDEWAY PORTION, THE BODY HAVING A LONDITUDINAL SLOT FORMED THEREIN ALONG THE REMAINING SIDE OF THE GUIDEWAY AND EXTENDING FORWARDLY FROM THE REAR END OF THE BODY, A BRUSH TERMINAL EXTENDING THROUGH THE LONGITUDINAL SLOT FOR RECEIPT IN THE REAR GUIDEWAY PORTION FOR ELECTRICAL CONNECTION TO THE BRUSH, A SPRING IN THE REAR GUIDEWAY PORTION FOR MAINTAINING THE BRUSH TERMINAL IN ELECTRICAL PORTION WITH THE BRUSH, THE INTERNAL SHOULDERS COACTING WITH THE SPRING TO ENGAGE THE BRUSH TERMINAL THEREBETWEEN AND TO FIRMLY RETAIN THE BRUSH TERMINAL WITHIN THE REAR GUIDEWAY PORTION AFTER THE BRUSH IS COM PLETELY WORN, AND A SNAP-ON COVER OF NONCONDUCTIVE MATERIAL REMOVABLY MOUNTED ON THE REAR OF THE BODY FOR CLOSING THE SAME AND PROVIDING A SEAT FOR THE SPRING.
 2. THE BRUSH ASSEMBLY OF CLAIM 1 WHEREIN THE LONGITUDINAL SLOT IN THE BRUSH HOLDER IS CONTAINED IN A PLANE PERPENDICULAR TO THE LEADING AND TRAILING OF THE BRUSH. 